Reliability of safety devices for example to automatically shut down electric equipment in case of errors, e.g. excessive heating, in order to avoid damage, fire, or personnel accidents, is an increasing concern and requirement.
A conventional way to improve reliability of the safety devices themselves has been to duplicate the error detecting circuit and thereby provide a redundant system with two evaluation channels operating in parallel on the measurement signal from a thermistor in the electric equipment. Such a system is redundant only to non-typical component faults in one of the evaluation channels. In more sophisticated systems the two evaluation channels have been implemented with fundamentally different technology, but still receive the same thermistor signal and compare to the same reference value, thereby still limiting the redundancy effect to the evaluation components themselves.